Circuits for electromagnetic devices



CIRCUITS FOR ELECTROMAGNETIC DEVICES Filed March 23, 1927 Arron/m Patented June 16; 1931 g HOB-ACE 1WHITTLE; or mnrnnwoon, ew, JERSEY, 'nssi'eivon ro BELL TELEPHONE a. LABoRAroRIns :inconronarnn, or new ,Yonm; N. Y.,;A v conronarron on NEW crnotrirsron f ps wso wmc'psvicssi." f

application filed Eiliarch 2'3; 1e27, serial m3. 177,818 f,

This invention relates to circuits for electromagnetic devices" and particularly *to" means for neutralizing steady flux in electro magnetic devices coupled to 'direct c-urrent 10 through one of the transformer windings;

The flux setup in the transformer core due s to the. direct current fiowingthrough aWiIICl I ing thereof. is in many cases undesirable, espec1ally 1n the case of cores wh ch satu- 15 rate at a lowflux density; such as those made of certain nickel iron alloys which are-dis-' closed in PatentNo'. l,5 86,884 granted to e; w. Elmen, June 1, 1926. j' a The present invention overcomes advantage and is applicablenotuonly to trans former circuits but to other e'lectromagnetic systems. An important application is in out;

put circuits of vacuum'tube amplifiersf'lhis 1 application of the invention has been chosen 5 to illustrate the invention and is described at length; below. There is providedanout put transformer having an auxiliary wind; A ing connected to the source of space current i for, setting up. a magnetoniotiveforce inthe transformer core which opposes the mega netomotivei force'set up thedirect current flowing in v the primary; winding from 1 this i source and which, therefore, dec e ses the flux-in the transformer core. hen using a core of the nickel-iron alloy referred "to above, it is preferable to have these Inag'netomotive. forcesfsnbstantially equal and oppo-i site, thusreducingthe steadysflux' inthe core to zero 'or'thereaboutfsothat high .permea T bility in 'the'core material isobtai'ned, -lresulting in high mutual ,inductancejin'the transformer and therefore lowphasedistoras I p I p v V V I A I i 6i and 12gare equalythen, in order that the magnet mos e rorces set up in the comet tion and high efiicie ncy Theiinvention may befully understood referring to thefollowing description taken in connection with: the accompanying drawing which is a diagrammatic showing of the embodiment of the inventionfmentioned just Referring now to the drawing, theinputf circuitis connected between the grid or cone 01 electrode 4 and the cathode 2 of an electron discharge device or vacuum tube l, while a winding 6 of transformer 7 is connected between the anode 3 and the cathode 2 through a choke coil 8 and a battery 9. 1 An other transformer winding 10 isconnected to a load'l-l'. r A third transformer winding 12 woundin the same direction'as the'wind-v ing ,6, is connected to the battery 9 through A condenser. 14,-is connected across the bat low impedance path between" the transformer winding 6 and-the cathode 2;

'Inconsidering the operation ofthe device, v

the choke coil 8 and a resistance element 13. I

'tery9 and choke coil'8 so as to provide-aj it is seenthat direct current flows from the positive terminal ofloattery-9 through choke r coil 8, transformer/winding 6 and thence fromthe anode '3 to cathode 2 of the vacuum tube 1, this" cathode being connected to the negative-terminal of battery '9; Direct current also" flows from the positive'terminal of 7 battery 9 through-chokecoile, transformer I winding 12, resistance element-13 and thence to thejnegative battery terminal. Since the fwindingsiti' and 12 min the same direction 7 and the currents flow through thesewindingsv in opposite directions it'is clear that the magnetomotive forces setynpin the transformer, core due to these't'wo windings are opposed to eachother. The 'ratioo-f the turns ofwind- 'ings 6 and'1 2 and the resistance ofthe ele- V mentj 13 may be made suchthat any'desired fiux'flows in thecore of tra'nsformer 7. When employing a core material such as a nickelironf,alloyfiwhich saturates "at a low flux de ansity it is desirable to make theinagnetomotive'fo'rcesfset upFb y the'windings 6 and 12,- respectively; approximately equal and oppositeso thatsub'stantially no flux: flows in thecore. If thenumberof turns of windings internalresista-nce of the vacuulntube 1 meas :ured between theanodef 3 and the cathode 2. Whengthe'turns ofwinding 12 are less than those'of winding 6, the resistance of element 13 must be decreased in order that the ampere turns of and, therefore, the magnetomotive forces set up by the windings 6 and 12, respectively, may be equal. It is apparent that as the turns of winding 12 are decreased, the alternating current efiiciency of the transformer is increased, but the battery drain is simultaneously increased and vice versa. Since the anode current of most electron discharge devices is comparatively small, it is ordinarily desirable to make the turns of the winding 6 in the anode circuit two or three times as great as the turnsin the auxiliary winding 12 so as to make the transmission loss due to the use of the auxiliary winding negligible. \Vhere there is no necessity for preventing phase distortion in the trans former, a choke coil maybe connected in series with the resistance 13 for the purpose of increasing the alternating current efficiency of the transformer.

While the invention has beendescribed in connection with a transformer, it is apparent that thereare numerous other applications therefor, for instance, telephone receivers, measuring instruments, and other electromagnetic devices. Moreover, the invention isinot limited tov a circuit employing an electron discharge device for supplying alternating current to the electromagnetic device, but is applicable to any circuit arrangement em loying a device which is to be supplied wit current from a direct current source as, for instance, a telephone transmitter. In

some cases, as when employing an electromagnetic device having a magnetic circuit of amaterial other than the nickel-iron alloy referred to above,-it may not be desirable to inga plurality of windings, a source of direct current connected to one of said windings, a

vacuum tube in series with said source and said winding, a second winding connected in circuit with a source ofdirect current so that the magnetomotive forces set up by the currents flowing in said windings are opposed to each other, said last mentioned winding hav- *ing substantially fewer turns than said one WlIldlIlg anda resistance connected to one of said windings for reducing the current flowing therein, and thereby altering the flux in the transformer core, so that the magnetomotive forces set up by the direct currents flowing in said windings substantially neutralize each other.

2. In combination, an electron discharge device having an anode and a cathode, means for impressing signals thereon, and an elecsource as the only source of voltage external to said winding.

3. In combination, an electron discharge 1 device having an anode, a cathode and a control electrode, a transformer,,a source of di-. rect current connected between said cathode. and anode through one winding of said transformer,'means for impressing signals on said: winding, a second winding on said transformer having substantially fewer turns than said one winding andconnected to a direct.

current source such that the magnetomotive force set up in the core of said transformer by said second mentioned windingis substantially equal and opposite to the magnetomotive force set up by the direct current flowing through said first mentionedwinding, thereby reducing the direct current flux in said core substantially to zero, saidsecondmentioned winding being included in a circuit containing only impedance which remains constant as regards signal variations and a direct current-source'as the onlysource of voltage external tosaid winding.

4. In combination, an electron discharge device having an anode, a cathode and a control electrode, a transformer having a plurality of windings, a source of directcurrent, the'negative terminal of which is connected to said cathode and a positive terminal. of which is connected to a common terminal of two of said transformer windings,.the.

7 other terminal of one of said windings bebeing connectedto said negative battery terminal, said second mentioned'winding having substantially fewer turns thansaid one winding.

5. In combination, an electron discharge device having an anode, a cathode and a controlelectrode, a transformer having a plurality of windings, a source of direct current, the

negative terminal of which-is connectedto saidcathode, and a positive terminal of which is connected to a common terminal of two of said transformer windlngs, the other-term1-- 11-: .1ng connected to said anode and the other terminal of said second mentioned winding nal of one of said windings being connected l 12% to said anode and the other terminal of a second winding being connectedto said-negative battery terminal through a resistance, element, said second winding having sub stantially fewer turns than said one winding,

the resistance of said resistance element, the

ratio of the turns of said transformer wind ings and the directionof the currentsflowing in said windings being such that substantial{ 1y no directcurrent flux'fiows in the core of said transformer. v

6. A circuit comprising a transformer having a plurality of windings,one of said'winding having a substantially greater number of turns than another of said windings, a core for said transformena source of direct cur negative with respect'to the potential of the said one terminalofthe said other wind ing.

9. In a si nalin 's stem a line over'which I, a z s gnal currents are transnntted, an electrical network connected to :said line and having a direct cu'rrentpath, an inductance device comprisinga coreand a plurality of windings thereon, one of said windings connected throughithe direct current path of said network to a source of direct current, and means for substantially neutralizing the magneto-, A

motive force produced in said core by direct current through saidone winding, said last mentionedmeans comprising another of said windings having from one-half to one-third as many turns as said one winding,a connec? tion fromoneftermlnal of said other winding J to one term nal of said one wlndlng, and a connection from the other terminal of said other winding to a potential which is negative with respect to the potential of the said one terminal of said other winding. 7

In witness whereof, I hereunto subscribe my name this 17th day of March A. 1)., 1927. 5 HORACE WHITTLE.

and a transformer, said transformer having a core and a plurality of windings thereon, 1 one portion of said circuitincludingsaid c vacuum tube, said direct current source, and

one of said windings having a certaincnurnv I ber of turns, the current in said portion pro-v ducing a certain magnetomotive force in said core in one direction, and a second portion of said circuit including said resistance, said di- I rect current source and anotherfof saidwind- I ings having from one-halfto one-"third as many turns as said first winding, said resist ance adjusting the current in said second-par tion to produce a magnetomotive'force'in saidv c core in the opposite direction to substantially balance out said first mentioned magnetomotive force. 7 I P 8. In a signal repeating system, a ther mionic discharge device having at least three elements, means for impressing signal voltage variations on said discharge device, an -in V ductance device comprising a core and a plurality of windings thereon,oneofv said windings connected tothe' output circuit of said dischargedevice, means for impressing a direct current potential on the anode of said discharge device through saidone winding, and means for neutralizing, at least in part, the magnetomoti've force produced in said core by the direct current through said one I winding, said last mentioned means comprising another of said windings having substan tially fewer turns than said one winding, a

' connection from one terminal of said other winding to one terminal of said onev winding and a connectionefrom the other terminal of said other winding to a potential which is, 7 

